A US strike has killed 21 civilians near the ISIS-held city of Raqqa, a UK-based monitoring group said on Monday.

The so-called Syrian Observatory for Human Rights said that 21 civilians were killed during a US airstrike while they were trying to flee the ISIS de facto Capital in Syria.

ISIS seized Raqqa in 2014, the same year when it started its campaign of terror in Syria. It then proceeded to capture large swathes of Syrian territory.

“The civilians were boarding small boats on the northern bank of the Euphrates River to flee southern neighborhoods of Raqqah,” said observatory Director Rami Abdel Rahman. He added that women and children were among the casualties.

“The toll may continue to rise as some of the wounded are in critical condition,” he noted.

According to latest figures released by SOHR, airstrikes by the US and its allies left a total of 225 civilians dead in Syria between April 23 and May 23 alone.

On Friday, the US-led military coalition, technically known as Operation Inherent Resolve, announced that its airstrikes had killed 484 civilians in Syria and Iraq, another Arab country in which it carries out airstrikes against purported ISIS targets.

But Airwars, a journalist-led transparency project that monitors and assesses civilian casualties from international airstrikes in Iraq, Syria and Libya, estimated that the toll was 7 times higher. The group found that at least 3,100 civilians were killed in American-led airstrikes from August 2014 to March 2017.

Much of the increase in the Airwars data coincided with the operations to retake Mosul, Iraq, the ISIS’s largest stronghold, and Raqqa, Syria, the group’s de facto capital.

Syria urges UN, UNSC to stop US-led airstrikes

Syria harshly slammed US repeated airstrikes in the Arab country, calling on the United Nations and the international body’s Security Council to prevent the Washington-led coalition form killing Syrian civilians and destroying the country’s infrastructure.

In two letters to UN Secretary General Antonio Guterres and the head of UN Security Council on Sunday, Syria’s Foreign Ministry lambasted the US-led coalition’s airstrikes in Syria’s northern city of Raqqah, which killed at least 43 people in the Jomeili neighborhood.

The ministry said the “crimes” committed by the so-called military alliance are no way less than those perpetrated by the ISIS terrorist group against the Syrian civilians. It also said, in the pair of letters, that the airstrikes directly target country’s infrastructure, “including bridges, oil and gas wells, dams, electricity and water plants, and public and private buildings.”

US downplays civilian casualties as ‘fact of life’

US Defense Secretary James Mattis in a bid to justify civilian death caused by the so-called anti-ISIS coalition’s airstrikes in Iraq and Syria, said such casualties are merely “fact of life”.

Explaining on reasons behind appalling civilian death, US Defense Secretary told CBS on 29 may that Washington’s has shifted its tactic against the terror group from “attrition” to “annihilation.”

“We have already shifted from attrition tactics, where we shove them from one position to another in Iraq and Syria, to annihilation tactics, where we surround them. Our intention is that the foreign fighters do not survive the fight to return home,” Mattis claimed.

“Civilian casualties are a fact of life in this sort of situation,” the Pentagon chief added, boasting that “We’ve had success on the battlefield.”

The US and a number of its allies have been pounding parts of Iraq and Syria since 2014. The campaign has yet to yield any meaningful achievements besides destroying hospitals and other critical infrastructure.